Final answer:
The blade or cylinder placed in the jawbone during dental implant surgery is the Implant fixture. It serves as the foundation for the replacement tooth, to which the abutment and crown are later attached.
Step-by-step explanation:
The blade or cylinder that is surgically embedded into the bone during the first stage of dental implant surgery is known as the C) Implant fixture. An implant fixture is placed within the jawbone and acts as a strong foundation for the replacement tooth. After the implant fixture integrates with the bone tissue, a process known as osseointegration, additional components like the abutment and crown can then be attached. The abutment serves as an intermediary between the implant and the crown, and the crown is the visible part that resembles a natural tooth.